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  • Calling Subclass Method in Java

    - by destructo_gold
    Given the following situation (UML below), If Y has the method: public void PrintWs(); and X has: ArrayList <P> myPs = new ArrayList(); Y y = new Y(); Z z = new Z(); myPs.add(y); myPs.add(z); How do I loop through each myPs object and call all Ys PrintWs (without using instanceof)? http://starbucks.mirror.waffleimages.com/files/68/68c26b815e913acd00307bf27bde534c0f1f8bfb.jpg

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  • JNI on Android, how to pass int from c to java

    - by Joaquin
    I have a C function, I simply returns an integer, as follows: JNIEXPORT jint JNICALL Java_org_project_ScreenPosition(JNIEnv* env, jobject thiz){ int i=1; return i; } I call this function in the way of an Activity onCreateContextMenu Android, as follows: public void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo){ menu.setHeaderTitle("TryMenu"); int a=ScreenPosition(); return; } But all crash

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  • Strange/simple batch question regarding Java/Ant

    - by Monster
    For my company, I'm making a batch script to go through and compile the latest revisions of code for our current project. I'm using Ant to build the class files, but encountered a strange error. One of the source files imports .* from a directory, where there are no files (only folders), and in fact, the folders needed are imported right after. It compiles perfectly fine in Eclipse, but I'm using an Ant script to automate it outside of the IDE, and Javac throws an error when it encounters this line. Is there any automated procedure I can use to ignore/suppress this error with javac in Ant? I'd even go so far as to create a dummy file in the importing directory, but all of that in contained in a Jar file I don't wish to have to decompress and then recompress with the dummy file. Thanks!

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  • Are there any other Java schedulers besides Quartz(FOSS) and Flux(Commercial)

    - by mP
    I am interested in finding out about other job scheduling packages besides Quartz and Flux. Given the plethora of web frameworks i find it perculiar that there is really only one scheduler. Are there others that perhaps are very much unknown/unpopular ? Spring Batch Not really a scheduling solution but rather a batch job coordinator etc. http://static.springsource.org/spring-batch/faq.html#schedulers How does Spring Batch differ from Quartz? Is there a place for them both in a solution? Spring Batch and Quartz have different goals. Spring Batch provides functionality for processing large volumes of data and Quartz provides functionality for scheduling tasks. So Quartz could complement Spring Batch, but are not excluding technologies. A common combination would be to use Quartz as a trigger for a Spring Batch job using a Cron expression and the Spring Core convenience SchedulerFactoryBean .

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  • Pass string between two threads in java

    - by geeta
    I have to search a string in a file and write the matched lines to another file. I have a thread to read a file and a thread to write a file. I want to send the stringBuffer from read thread to write thread. Please help me to pass this. I amm getting null value passed. write thread: class OutputThread extends Thread{ /****************** Writes the line with search string to the output file *************/ Thread runner1,runner; File Out_File; public OutputThread() { } public OutputThread(Thread runner,File Out_File) { runner1 = new Thread(this,"writeThread"); // (1) Create a new thread. this.Out_File=Out_File; this.runner=runner; runner1.start(); // (2) Start the thread. } public void run() { try{ BufferedWriter bufferedWriter=new BufferedWriter(new FileWriter(Out_File,true)); System.out.println("inside write"); synchronized(runner){ System.out.println("inside wait"); runner.wait(); } System.out.println("outside wait"); // bufferedWriter.write(line.toString()); Buffer Buf = new Buffer(); bufferedWriter.write(Buf.buffers); System.out.println(Buf.buffers); bufferedWriter.flush(); } catch(Exception e){ System.out.println(e); e.printStackTrace(); } } } Read Thraed: class FileThread extends Thread{ Thread runner; File dir; String search_string,stats; File Out_File,final_output; StringBuffer sb = new StringBuffer(); public FileThread() { } public FileThread(CountDownLatch latch,String threadName,File dir,String search_string,File Out_File,File final_output,String stats) { runner = new Thread(this, threadName); // (1) Create a new thread. this.dir=dir; this.search_string=search_string; this.Out_File=Out_File; this.stats=stats; this.final_output=final_output; this.latch=latch; runner.start(); // (2) Start the thread. } public void run() { try{ Enumeration entries; ZipFile zipFile; String source_file_name = dir.toString(); File Source_file = dir; String extension; OutputThread out = new OutputThread(runner,Out_File); int dotPos = source_file_name.lastIndexOf("."); extension = source_file_name.substring(dotPos+1); if(extension.equals("zip")) { zipFile = new ZipFile(source_file_name); entries = zipFile.entries(); while(entries.hasMoreElements()) { ZipEntry entry = (ZipEntry)entries.nextElement(); if(entry.isDirectory()) { (new File(entry.getName())).mkdir(); continue; } searchString(runner,entry.getName(),new BufferedInputStream(zipFile.getInputStream(entry)),Out_File,final_output,search_string,stats); } zipFile.close(); } else { searchString(runner,Source_file.toString(),new BufferedInputStream(new FileInputStream(Source_file)),Out_File,final_output,search_string,stats); } } catch(Exception e){ System.out.println(e); e.printStackTrace(); } } /********* Reads the Input Files and Searches for the String ******************************/ public void searchString(Thread runner,String Source_File,BufferedInputStream in,File output_file,File final_output,String search,String stats) { int count = 0; int countw = 0; int countl=0; String s; String[] str; String newLine = System.getProperty("line.separator"); try { BufferedReader br2 = new BufferedReader(new InputStreamReader(in)); //OutputFile outfile = new OutputFile(); BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(output_file,true)); Buffer Buf = new Buffer(); //StringBuffer sb = new StringBuffer(); StringBuffer sb1 = new StringBuffer(); while((s = br2.readLine()) != null ) { str = s.split(search); count = str.length-1; countw += count; if(s.contains(search)){ countl++; sb.append(s); sb.append(newLine); } if(countl%100==0) { System.out.println("inside count"); Buf.setBuffers(sb.toString()); sb.delete(0,sb.length()); System.out.println("outside notify"); synchronized(runner) { runner.notify(); } //outfile.WriteFile(sb,bufferedWriter); //sb.delete(0,sb.length()); } } } synchronized(runner) { runner.notify(); } br2.close(); in.close(); if(countw == 0) { System.out.println("Input File : "+Source_File ); System.out.println("Word not found"); System.exit(0); } else { System.out.println("Input File : "+Source_File ); System.out.println("Matched word count : "+countw ); System.out.println("Lines with Search String : "+countl); System.out.println("Output File : "+output_file.toString()); System.out.println(); } } catch(Exception e){ System.out.println(e); e.printStackTrace(); } } }

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  • Python vs. Java performance (runtime speed)

    - by Bijan
    Ignoring all the characteristics of each languages and focusing SOLELY on speed, which language is better performance-wise? You'd think this would be a rather simple question to answer, but I haven't found a decent one. I'm aware that some types of operations may be faster with python, and vice-versa, but I cannot find any detailed information on this. Can anyone shed some light on the performance differences?

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  • Create A Java Variable (String) of a specific size (MB's)

    - by Bernie Perez
    I am trying to benchmark some code. I am sending a String msg over sockets. I want to send 100KB, 2MB, and 10MB String variables. Is there an easy way to create a variable of these sizes? Currently I am doing this. private static String createDataSize(int msgSize) { String data = "a"; while(data.length() < (msgSize*1024)-6) { data += "a"; } return data; } But this takes a very long time. Is there a better way?

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  • Java - Is Set.contains() broken on OpenJDK 6?

    - by Peter
    Hey, I've come across a really strange problem. I have written a simple Deck class which represents a standard 52 card deck of playing cards. The class has a method missingCards() which returns the set of all cards which have been drawn from the deck. If I try and compare two identical sets of missing cards using .equals() I'm told they are different, and if I check to see if a set contains an element that I know is there using .contains() I am returned false. Here is my test code: public void testMissingCards() { Deck deck = new Deck(true); Set<Card> drawnCards = new HashSet<Card>(); drawnCards.add(deck.draw()); drawnCards.add(deck.draw()); drawnCards.add(deck.draw()); Set<Card> missingCards = deck.missingCards(); System.out.println(drawnCards); System.out.println(missingCards); Card c1 = null; for (Card c : drawnCards){ c1 = c; } System.out.println("C1 is "+c1); for (Card c : missingCards){ System.out.println("C is "+c); System.out.println("Does c1.equal(c) "+c1.equals(c)); System.out.println("Does c.equal(c1) "+c.equals(c1)); } System.out.println("Is c1 in missingCards "+missingCards.contains(c1)); assertEquals("Deck confirm missing cards",drawnCards,missingCards); } (Edit: Just for clarity I added the two loops after I noticed the test failing. The first loop pulls out a card from drawnCards and then this card is checked against every card in missingCards - it always matches one, so that card must be contained in missingCards. However, missingCards.contains() fails) And here is an example of it's output: [5C, 2C, 2H] [2C, 5C, 2H] C1 is 2H C is 2C Does c1.equal(c) false Does c.equal(c1) false C is 5C Does c1.equal(c) false Does c.equal(c1) false C is 2H Does c1.equal(c) true Does c.equal(c1) true Is c1 in missingCards false I am completely sure that the implementation of .equals on my card class is correct and, as you can see from the output it does work! What is going on here? Cheers, Pete

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  • Java KeyListener in separate class

    - by Chris
    So I have my main class here, where basically creates a new jframe and adds a world object to it. The world object is basically where all drawing and keylistening would take place... public class Blobs extends JFrame{ public Blobs() { super("Blobs :) - By Chris Tanaka"); setVisible(true); setResizable(false); setSize(1000, 1000); setIgnoreRepaint(true); setDefaultCloseOperation(EXIT_ON_CLOSE); add(new World()); } public static void main(String[] args) { new Blobs(); } } How exactly would you get key input from the world class? (So far I have my world class extending a jpanel and implementing a keylistener. In the constructor i addKeyListener(this). I also have these methods since they are auto implemented: public void keyPressed(KeyEvent e) { if (e.getKeyCode() == KeyEvent.VK_W) System.out.println("Hi"); } public void keyReleased(KeyEvent e) {} public void keyTyped(KeyEvent e) {} However this does not seem to work?

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  • Reading in bytes produced by PHP script in Java to create a bitmap

    - by Kareem
    I'm having trouble getting the compressed jpeg image (stored as a blob in my database). here is the snippet of code I use to output the image that I have in my database: if($row = mysql_fetch_array($sql)) { $size = $row['image_size']; $image = $row['image']; if($image == null){ echo "no image!"; } else { header('Content-Type: content/data'); header("Content-length: $size"); echo $image; } } here is the code that I use to read in from the server: URL sizeUrl = new URL(MYURL); URLConnection sizeConn = sizeUrl.openConnection(); // Get The Response BufferedReader sizeRd = new BufferedReader(new InputStreamReader(sizeConn.getInputStream())); String line = ""; while(line.equals("")){ line = sizeRd.readLine(); } int image_size = Integer.parseInt(line); if(image_size == 0){ return null; } URL imageUrl = new URL(MYIMAGEURL); URLConnection imageConn = imageUrl.openConnection(); // Get The Response InputStream imageRd = imageConn.getInputStream(); byte[] bytedata = new byte[image_size]; int read = imageRd.read(bytedata, 0, image_size); Log.e("IMAGEDOWNLOADER", "read "+ read + " amount of bytes"); Log.e("IMAGEDOWNLOADER", "byte data has length " + bytedata.length); Bitmap theImage = BitmapFactory.decodeByteArray(bytedata, 0, image_size); if(theImage == null){ Log.e("IMAGEDOWNLOADER", "the bitmap is null"); } return theImage; My logging shows that everything has the right length, yet theImage is always null. I'm thinking it has to do with my content type. Or maybe the way I'm uploading?

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  • Java: how to name boolean properties

    - by NoozNooz42
    I just had a little surprise in a Webapp, where I'm using EL in .jsp pages. I added a boolean property and scratched my head because I had named a boolean "isDynamic", so I could write this: <c:if test="${page.isDynamic}"> ... </c:if> Which I find easier to read than: <c:if test="${page.dynamic}"> ... </c:if> However the .jsp failed to compile, with the error: javax.el.PropertyNotFoundException: Property 'isDynamic' not found on type com... I turns out my IDE (and it took me some time to notice it), when generating the getter, had generated a method called: isDynamic() instead of: getIsDynamic() Once I manually replaced isDynamic() by getIsDynamic() everything was working fine. So I've got really two questions here: is it bad to start a boolean property's name with "is"? wether it is bad or not, didn't IntelliJ made a mistake here by auto-generating a method named isDynamic instead of getIsDynamic?

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  • Java JEditorPane

    - by ikurtz
    ChatGUI im using 2 JEditorPane to transfer text from one to another. once i have transfered the data i do the following: JEditorPane.setText(null); JEditorPane.setCaretPosition(0); but as you can see from the attached image the return action makes the prompt appear a row down. how can i fix this?

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  • Java - JPA - @Basic and @Embedded

    - by Yatendra Goel
    I am learning JPA from this tutorial. I have some confusions in understanding the following annotations: @Basic @Embedded Fields of an embeddable type default to persistent, as if annotated with @Embedded. If the fields of embeddable types defualt to persistent, then why would we need @Embedded

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  • Loading data in constructors and not in constructors [JAVA]

    - by Richeve S. Bebedor
    i just want to know the difference between loading the data inside the constructor and loading the data outside the constructor but not inside any methods example: Loading inside constructor public class Model{ Object testobject; public Model(){ testobject=new Object(); } } VS example: Loading outside constructor public class Model{ Object testobject=new Object(); public Model(){ } }

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  • Java: Set<E> collection, where items are identified by its class

    - by mschayna
    I need Set collection, where its items will be identified by items class. Something like ReferenceIdentityMap from Appache Collections, but on class scope i.e. two different instances of same class must be identified as same in this collection. You know, it is a violation of equals()/hashCode() identity principle but in occasional use it makes sense. I have done this in simple class backing with Map<Class<? extends E>, E>, but due to simplicity it doesn't implement Set<E>. There may be a more elegant solution, decorator of any Set<E> would be great. Is there any implementation of such collection there (Apache/Google/something/... Collections)?

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  • Question about layout in java.

    - by extro
    I have two panels main_panel and child_panel. I have set layout for main_panel by using "main_panel.setLayout(flowlayout)" and added child_panel in main_panel by using "main_panel.add(child_panel)". This child_panel gets added to main_panel but its position is at the cross-section of horizontal midpoint and top vertical section of screen. But I want child_panel to be at the top left corner, something I could have done by using "child_panel.setlocation(a,b)" method, if I have set the Layout of main_panel as NULL. I have used flowlayout here because I want components in the JPanel to keep adjusting with the size of JFrame. So question is, can I add child_panel to main_panel at the exact location I want, even if I set the Layout of main_panel as not NULL.

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  • Problem loading java properties

    - by markovuksanovic
    I am trying to load properties from a file (test.properties) The code I use is as follows: URL url = getClass().getResource("../resources/test.properties"); properties.load(url.openStream()); But when executing the second line I get a NPE. (null pointer exception) I'm not sure what's wrong here... I have checked that the file exists at the location where URL points to... Any help is appreciated....

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  • Java threadpool functionality

    - by cpf
    Hi stackoverflow, I need to make a program with a limited amount of threads (currently using newFixedThreadPool) but I have the problem that all threads get created from start, filling up memory at alarming rate. I wish to prevent this. Threads should only be created shortly before they are executed. e.g.: I call the program and instruct it to use 2 threads in the pool. The program should create & launch the first 2 Threads immediately (obviously), create the next 2 to wait for the previous 2, and at that point wait until one or both of the first 2 ended executing. I thought about extending executor or FixedThreadPool or such. However I have no clue on how to start there and doubt it is the best solution. Easiest would have my main Thread sleeping on intervals, which is not really good either... Thanks in advance!

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  • java: how to convert a file to utf8

    - by Enrique San Martín
    Hi, i have a file that have some non-utf8 caracters (like "ISO-8859-1"), and so i want to convert that file (or read) to UTF8 encoding, how i can do it? The code it's like this: File file = new File("some_file_with_non_utf8_characters.txt"); /* some code to convert the file to an utf8 file */ ... edit: Put an encoding example

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  • Mix of Arabic and English causes problems in JTextArea (Java)

    - by Dan
    I have a JTextArea which displays HTML of an Arabic web page. So it's essentially a mix of English and Arabic. In the JTextArea, with columns set to 30, certain text just disappears instead of wrapping properly. The weird thing is that if I copy the invisible text and paste it into Notepad, then I can see it in Notepad. If I change the number of columns to 40, everything displays fine. Any ideas?

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  • Read Java in as Hex

    - by James
    Hi, I have tried to solve this but I keep coming up with stuff that is no help I'm sure this is easy (when you know how of course ;) ) What I would like to do is read in a file using a byte stream like below: while((read = in.read()) != -1){ //code removed to save space Integer.toHexString(read); System.out.println(read); } When it prints out the Hex to the screen it will print out numbers fine e.g 31 13 12 0 but when it comes to a hex code that should be 01 31 it will print 0 131. I want to read it in to a variable like you would see in a hex editor i.e 00 11 21 31 no single numbers as i need to scan the whole file and look for patterns which I know how to do I'm just stuck on this :/ so in short i need a variabe to contain the two hex characters i.e int temp = 01 not int temp = 0 , I hope this all makes sense, I'm a little confused as it's 3am! If anyone knows how to do this I would be most greatful, p.s thanks for the help in advance this site has saved me loads of research and have learnt a lot! Many thanks.

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  • Deleting from arraylist and exporting back to .buab file(Java)

    - by Dave
    Ive made an address book. I can currently write to the arraylist and save it back to the .buab file, but I cant delete from the arraylist and export it back to the .buab file? Im pretty much stuck on this. Im able to retrive contacts from the .buab and scroll through them using the JTextFields and buttons ive created. Any help will be dearly appreciated. Ive set up seprate classes for all operations (newcontacts, nextcontact etc). If you need the code posted let me know.. Cheers Dave

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